﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using DME.Json.Utilities;
using System.Reflection;

namespace DME.Json.Converters
{
    /// <summary>
    /// Converts a <see cref="KeyValuePair{TKey,TValue}"/> to and from JSON.
    /// </summary>
    public class KeyValuePairConverter : JsonConverter
    {
        /// <summary>
        /// Writes the JSON representation of the object.
        /// </summary>
        /// <param name="writer">The <see cref="JsonWriter"/> to write to.</param>
        /// <param name="value">The value.</param>
        /// <param name="serializer">The calling serializer.</param>
        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            Type t = value.GetType();
            PropertyInfo keyProperty = t.GetProperty("Key");
            PropertyInfo valueProperty = t.GetProperty("Value");

            writer.WriteStartObject();
            writer.WritePropertyName("Key");
            serializer.Serialize(writer, ReflectionUtils.GetMemberValue(keyProperty, value));
            writer.WritePropertyName("Value");
            serializer.Serialize(writer, ReflectionUtils.GetMemberValue(valueProperty, value));
            writer.WriteEndObject();
        }

        /// <summary>
        /// Reads the JSON representation of the object.
        /// </summary>
        /// <param name="reader">The <see cref="JsonReader"/> to read from.</param>
        /// <param name="objectType">Type of the object.</param>
        /// <param name="existingValue">The existing value of object being read.</param>
        /// <param name="serializer">The calling serializer.</param>
        /// <returns>The object value.</returns>
        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            IList<Type> genericArguments = objectType.GetGenericArguments();
            Type keyType = genericArguments[0];
            Type valueType = genericArguments[1];

            reader.Read();
            reader.Read();
            object key = serializer.Deserialize(reader, keyType);
            reader.Read();
            reader.Read();
            object value = serializer.Deserialize(reader, valueType);
            reader.Read();

            return ReflectionUtils.CreateInstance(objectType, key, value);
        }

        /// <summary>
        /// Determines whether this instance can convert the specified object type.
        /// </summary>
        /// <param name="objectType">Type of the object.</param>
        /// <returns>
        /// 	<c>true</c> if this instance can convert the specified object type; otherwise, <c>false</c>.
        /// </returns>
        public override bool CanConvert(Type objectType)
        {
            if (objectType.IsValueType && objectType.IsGenericType)
                return (objectType.GetGenericTypeDefinition() == typeof(KeyValuePair<,>));

            return false;
        }
    }
}